Students in over 40 different countries (including the United States, and nations in Asia, Australia, Latin America, Africa, and Europe) were given this standardized test to measure which countries scored the highest.

The superintendent of America’s second-largest school district oversaw a $1.3 billion program to equip every student with an iPad. Now, questions over the bidding process and the program’s effectiveness have contributed to his resignation.

The company has appointed Marjorie Scardino, the former CEO of Pearson, to its formerly all-male board of directors. Scardino has a strong media background, something Twitter was expected to look for in a board candidate.